//
//  02_FirstTriangle.cpp
//  LearningOpenGL
//
//  Created by wangrui on 14-7-3.
//  Copyright (c) 2014年 PPS. All rights reserved.
//

// Include standard headers
#include <stdio.h>
#include <stdlib.h>

// Include GLEW
#include "glew.h"

// Include GLFW
#include "glfw3.h"
GLFWwindow* window;


#include "shader.hpp"

int main( void )
{
	// Initialise GLFW
	if( !glfwInit() )
	{
		fprintf( stderr, "Failed to initialize GLFW\n" );
		return -1;
	}
	
	glfwWindowHint(GLFW_SAMPLES, 4);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 2);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 1);
	
	
	// Open a window and create its OpenGL context
	window = glfwCreateWindow( 1024, 768, "Tutorial 02 - Red triangle", NULL, NULL);
	if( window == NULL ){
		fprintf( stderr, "Failed to open GLFW window. If you have an Intel GPU, they are not 3.3 compatible. Try the 2.1 version of the tutorials.\n" );
		glfwTerminate();
		return -1;
	}
	glfwMakeContextCurrent(window);
	
	// Initialize GLEW
	if (glewInit() != GLEW_OK) {
		fprintf(stderr, "Failed to initialize GLEW\n");
		return -1;
	}
	
	// Ensure we can capture the escape key being pressed below
	glfwSetInputMode(window, GLFW_STICKY_KEYS, GL_TRUE);
	
	// Dark blue background
	glClearColor(0.0f, 0.0f, 0.4f, 0.0f);
	
	// Create and compile our GLSL program from the shaders
	GLuint programID = LoadShaders( "SimpleVertexShader.vertexshader", "SimpleFragmentShader.fragmentshader" );
	
	// Get a handle for our buffers
	GLuint vertexPosition_modelspaceID = glGetAttribLocation(programID, "vertexPosition_modelspace");
	
	static const GLfloat g_vertex_buffer_data[] = {
		-1.0f, -1.0f, 0.0f,
		1.0f, -1.0f, 0.0f,
		0.0f,  1.0f, 0.0f,
	};
	
	GLuint vertexbuffer;
	glGenBuffers(1, &vertexbuffer);
	glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
	glBufferData(GL_ARRAY_BUFFER, sizeof(g_vertex_buffer_data), g_vertex_buffer_data, GL_STATIC_DRAW);
	
	do{
		
		// Clear the screen
		glClear( GL_COLOR_BUFFER_BIT );
		
		// Use our shader
		glUseProgram(programID);
		
		// 1rst attribute buffer : vertices
		glEnableVertexAttribArray(vertexPosition_modelspaceID);
		glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
		glVertexAttribPointer(
							  vertexPosition_modelspaceID, // The attribute we want to configure
							  3,                  // size
							  GL_FLOAT,           // type
							  GL_FALSE,           // normalized?
							  0,                  // stride
							  (void*)0            // array buffer offset
							  );
		
		// Draw the triangle !
		glDrawArrays(GL_TRIANGLES, 0, 3); // 3 indices starting at 0 -> 1 triangle
		
		glDisableVertexAttribArray(vertexPosition_modelspaceID);
		
		// Swap buffers
		glfwSwapBuffers(window);
		glfwPollEvents();
		
	} // Check if the ESC key was pressed or the window was closed
	while( glfwGetKey(window, GLFW_KEY_ESCAPE ) != GLFW_PRESS &&
		  glfwWindowShouldClose(window) == 0 );
	
	
	// Cleanup VBO
	glDeleteBuffers(1, &vertexbuffer);
	glDeleteProgram(programID);
	
	// Close OpenGL window and terminate GLFW
	glfwTerminate();
	
	return 0;
}



